For hydrogen-powered vehicle applications, the COMMISSION REGULATION (EU) No 406/2010 of 26 Apr. 2010 and implementing Regulation (EC) No 79/2009 of the European Parliament and of the Council on type-approval of hydrogen-powered motor vehicles have provisions that the components of the hydrogen supply of the vehicles must satisfy different tests. The valves must among others satisfy cyclic pressure tests. It is therefore wished that the valves for such applications can withstand a maximum static test pressure of 105 MPa (1050 bar) and a cyclic hydraulic pressure test of N=150 000 cycles with a cyclic pressure loading of 87.5 MPa and a nearly stress ratio R=min stress/max stress=0.
Prior art patent document published EP 2 548 984 A1 addresses the problem of a 6000 series aluminum alloy material that has to show a satisfactory resistance to hydrogen embrittlement. The material is intended to be used as material of storage container for high-pressure hydrogen gas. To that end this document discloses a specific composition of an aluminum alloy material. The behavior of this material with regard to hydrogen embrittlement is interesting. The resistance to cyclic pressure tests is however not sufficient for gas valve which comprises bore intersections with possible sharp edges which favor stress concentrations and the formation of cracks.
Prior art patent document published FR 1 176 960 is directed to a valve for very high pressures, i.e. up to and above 3 000 bar. The valve is designed so as to compensate the effort resulting from the pressure of the fluid against the moving closing element. The valve body is made of steel, more particularly of self-tempering steel with nickel, chrome and molybdenum. This document teaches that the body can be subject to an autofrettage treatment at a pressure of 10 000 bar for conferring a better mechanical behavior and a better dimensional stability. This teaching does not specify the type of applications to which the valve is directed and does not therefore address the problem of cyclic load. This teaching does not therefore provide a solution to the problem of cyclic pressure tests, in particular in connection with materials that are light and easy to machine, like aluminum, copper or brass.
Prior art patent document published DE 10 2009 000 538 A1 discloses the body of a connector for high pressure applications, in particular for applications in “common rail” diesel injection systems in combustion engines. The pressure in such systems is usually of above 1 000 bar. The connector is preferably made of stainless steel and is subject to an autofrettage treatment at a pressure of up to 15 000 bar. This treatment is intended to compensate the negative effect of stress concentrations in the sharp edges of bore intersections. There is however no mention of a resulting better behavior in fatigue in connection with a certain number of cycles.